J. Bio. Env. Sci. 2018

76 | Sadia et al.

RESEARCH PAPER OPEN ACCESS

Schiff base fluorescent-on ligand synthesis and its application

for selective determination of manganese in water samples

Maria Sadia*, Jehangir Khan, Robina Naz, Rizwan Khan

Department of Chemistry, University of Malakand, Chakdara, Dir (L),

Khyber Pakhtunkhwa, Pakistan

Article published on August 14, 2018

Key words: Novel Schiff base, Fluorescence turn-on, Ligand, Manganese, Fluorescence intensity

Abstract

Manganese contamination of water is becoming a serious health concern in recent years as even at lower levels of

exposure it is toxic for living organisms. Manganese can bind to functionally important domains of biomolecules

and thereby inactivates them. Therefore, a simple, sensitive and convenient method based on Schiff base

fluorescent turn-on ligand for determination of trace amount of manganese was developed in real water samples.

The novel Schiff base fluorescent turn-on ligand of 2-hydroxy-1-naphthaldehyde and 2-methoxybenzhydrazide

was synthesized and characterized using X-Ray Diffraction (XRD), Proton nuclear magnetic resonance (1HNMR)

and Fourier Transform Infrared Spectroscopic (FTIR) techniques. The ligand shows high selectivity and

sensitivity for manganese over other metals studied with 3.8 ×10-6 M limit of detection. Chelation with

manganese resulted in maximum enhancement in fluorescence intensity at pH 10 with 2:1 binding ratio of ligand

to manganese from Job's plot analysis and with 4×106 M-1 association constant from Benesi–Hildebrand plot.

*Corresponding Author: Maria Sadia mariasadia@gmail.com

Journal of Biodiversity and Environmental Sciences (JBES) ISSN: 2220-6663 (Print) 2222-3045 (Online)

Vol. 13, No. 2, p. 76-89, 2018

http://www.innspub.net

J. Bio. Env. Sci. 2018

77 | Sadia et al.

Introduction

Schiff base ligands have been extensively studied in

coordination chemistry mainly due to their facile

syntheses, easily tuneable steric, electronic properties

and good solubility in common solvents. Schiff bases

derived from a large number of carbonyl compounds

and amines have been used however, the studies on

their optical properties, such as fluorescence, are rare

(Arpi et al., 2006).

Schiff bases (imines) are known to be good ligands for

heavy metals. In addition, Schiff base derivatives

incorporating a fluorescent moiety are appealing tools

for optical sensing of toxic heavy metals (Lina et al.,

2010). Schiff bases with N and O as donor atoms are

well known to form strong complexes with heavy

metals (Morteza et al., 2010).

They have the potential to be used in different areas

such as electrochemistry, bioinorganic, catalysis,

metallic deactivators, separation processes, and

environmental chemistry. Moreover they are

becoming increasingly important in the

pharmacological, dye, and plastic industries as well as

in the field of liquid crystal technology (Ziyad et al.,

2011). Schiff bases derived from 2-hydroxy-1-

napthaldehyde have been extensively studied due to

their wide range of applications in medicinal field and

they form stable complexes with heavy metals due to

the presence of a phenolic hydroxyl group at their o-

position, which coordinates to the metal via

deprotonation (Nagesh et al., 2014).

Heavy metals are very toxic for living organisms even

at very low concentrations (Ghaedi et al.., 2009).

With the increasing use of a wide verity of metals in

industry and in our daily life, heavy metals are

intrinsic components of the environment.

Their presence is considered unique in the sense that

it is difficult to remove them completely from the

environment once they enter in it. Problems arising

from toxic heavy metal pollution of water have gained

serious dimensions (Santamaria, 2008).

Among the various heavy metals manganese is an

extremely toxic element naturally present in the

environment and also as a result of human activities

(Subhra et al.., 2008). Manganese is more frequently

of toxicological concern because it causes

neurodegenerative disorders (Janelle and Wei, 2008)

and is a severe poison for all living organisms (Castro

and Méndez, 2008). It causes diarrhoea, and is

carcinogenic and mutagenic (Duruibe et al.., 2007) in

nature.

Though several analytical methods including UV–Vis

spectroscopy, potentiometry, (Hosseini et al.., 2011)

flame atomic absorption spectrometric analysis,

(Rajesh and Madhoolika 2005) neutron activation

analysis (Aschner et al. 2006) and inductively

coupled plasma mass spectrometry (Dayu et al. 2008)

are generally used for determination of manganese in

waste water but these have limited use due to their

high limit of detection, difficulty in sample

preparation and costly instrumentation (Ya et al.

2014). In this paper, we describe the synthesis of

Schiff base fluorescent-on ligand N-((2

hydroxynaphthalene-1-yl) methylene)-2 methoxy

benzohydrazide and its fluorimetric application in the

determination of manganese in industrial waste water

samples.

Experimental

Chemicals and reagents

All chemicals and reagents used were of analytical

reagent grade purity and were purchased from

commercial sources. Analytical grade acetonitrile

solution and distilled water was used throughout the

experiments. 1×10-2 M stock solution of all required

mineral salts, 5×10-3 M ligand solution and working

solutions of low concentration were prepared by

appropriate dilution with distilled water.

Instrumentation

For FTIR spectra, the samples were prepared as KBr

pellets and the spectrum was obtained on FTIR

spectrophotometer Pretige 21 Shimadzu Japan in the

region 400–4000 cm-1. 1H NMR spectra of the

J. Bio. Env. Sci. 2018

78 | Sadia et al.

samples were obtained on Bruker Advance 400 MHz

spectrometer. X-ray structural analysis of the sample

was conducted using Bruker kappa APEXIICCD

diffractiometer. For the measurement of melting

points a Bicote Stuart-SMP 10 Japan was used. UV–

vis absorption spectroscopic measurements were

conducted on UV-visible 1800 spectrophotometer.

The emission spectra were monitored using

fluorescence spectrophotometer RF 5301 PC

Shimadzu Japan equipped with fluorescence free

quartz cuvettes of 1cm path length. Slit width were

5nm both for excitation and emission and a steady

state 150 W Xenon lamp was used as an excitation

source. The pH of the test solution was monitored by

a BANTE instrument pH meter. All measurements

were conducted at room temperature.

Synthesis of N-((2-hydroxynaphthalene-1-

yl)methylene)-2 methoxy benzohydrazide

The ligand was synthesized by modification of

literature method (Mengyu et al.., 2014) by dissolving

10 mmol (1.72 g) of 2-hydroxy-1-naphthaldehyde in

methanol, 2-3 drops of glacial acetic acid was added

into this solution and the solution was stirred for 10

minutes at room temperature. An equimolar amount

of 2-methoxybenzhydrazide 10 mmol (1.6618 g) was

added into this solution, the colour changed to bright

yellow and the reaction mixture was refluxed for 13

hours. Reaction progress was monitored by

establishing thin layer chromatography in ethyl

acetate and n-hexane (3:2) mixture. Afterward the

solvent was evaporated under reduced pressure and

the product was recrystallized in ethanol and pure

crystals of ligand were obtained. The whole scheme of

synthesis is shown in fig 1.

Results and discussions

Characterization by Fourier transform infrared

spectroscopy (FTIR)

In order to determine the functional group in the m

synthesized ligand FTIR spectroscopy was conducted

the data is given in table 1.

Table 1. FTIR spectral frequencies for ligand.

IR-band (C=N)

cm-1

IR-band

(C-OH)

cm-1

IR-band aliphatic

(-C-O)

cm-1

IR-band aromatic

(-C-H)

cm-1

IR-band aromatic

(C=C)

cm-1

1606 1260, 1217 1107, 1016 3035 1539,1505

Table 2. Crystal data and structure refinement for ligand.

Crystal parameters Values

Empirical formula, Formula weight C19H16N2O3, 320.34

Crystal system, Space group Monoclinic, P21/n

Temperature (K) 296

a, b, c, (Å) 7.1780 (18), 31.115 (8), 7.4635 (18)

β (o) 109.765 (8)

V (Å3) 1365.2 (4)

Z 4

Radiation type Mo Kα

µ (mm-1) 0.09

Crystal colour Yellow

crystal size (mm) (0.42 × 0.30 × 0.26)

Data collection

Diffractometer, scan mode Bruker kappa APEXIICCD, Multi-scan and ωscan

No of measured, independent and observed [I > 2σ(I)]

reflections

13509,3560,1502

Rint 0.082

(sin θ/λ)max (Å−1) 0.650

Refinements

R[F2 > 2σ(F2)], wR(F2), S 0.056, 0.161, 0.93

No. of reflections 3560

No. of restraints 2

H-atom treatment H-atom parameter constrained

Δ ρmax, Δρmin (e Å−3) 0.24, −0.26

J. Bio. Env. Sci. 2018

79 | Sadia et al.

In the region 400-4000 cm-1 several absorption

bands were observed in the FTIR spectrum of the

ligand. Assignments of characteristics bands

correspond to various functional groups present in

the ligand were made by comparison method. The

FTIR spectrum confirms the formation of imine bond

(-C=N) and no band assigned to (C=O) was detected.

Thus, the disappearance of carbonyl (-C=O) peak in

the region of 1700 cm-1 and appearance of the (-

C=N) peak in the region of 1606 cm-1 confirms the

formation of ligand.

Table 3. Comparison of ligand with already reported ligands.

Fluorophore Analyte Detection mode/

remarks

Optimal pH

range

Detection limit (M) Application Ref

1,10-phenanthroline

derivatives

Mn Enhancement 3.2-6.7 6.6×10−3 Water samples Wenling 2012

Rhodamine-based Mn, Cu Quenching 6.8-11 7.4 × 10-4 NA Jurriaan 2013

Arsenazo Mn Enhancement 2.4-6.4 3.9 × 10-5 NA Raju 2010

Asparagine

derivatives

Mn, Zn Quenching 5.7-8.9 4.2 × 10-4 NA Juyoung 2006

Deferoxamine Mn, Mg Enhancement 4.1-6.4 5.7 × 10-3 NA Claudia 2015

Hydrizide derivative Mn Enhancement 2-12 3.8 × 10-6 NA This work

The band at 3035 cm-1 corresponds to the

stretching vibration of aromatic-C-H. The spectrum

exhibit absorption band at 1539, 1505 and at 1260,

1217 cm-1 typically of aromatic-C=C and phenolic-O-H

stretching vibration. The bands at 1107 and 1016 cm-1

correspond to aliphatic-C-O (Tianzhi et al., 2008).

FTIR spectrum analysis of the ligand is shown in

figure [2].

Fig. 1. The proposed reaction scheme for the synthesis of N-((2-hydroxynaphthalene-1-yl)methylene)-2-

methoxybenzohydrazide, (ligand).

Characterization by single crystal X-ray diffraction

A single crystal of the ligand was grown from slow

evaporation of ethanol.

The solid state structure of ligand was confirmed by

single crystal X-ray diffraction. Ligand crystallized in

monoclinic unit cell of crystal system in which amine

J. Bio. Env. Sci. 2018

80 | Sadia et al.

moiety is twisted through 84.74o with respect to

naphthalene moiety. The geometry around N1 is

trigonal planner, showing that the lone pair of

nitrogen is involved in conjugation without disturbing

sp2 hybridization.

The bond distance between N1-C11 is 1.295 Å, N1-C12 is

1.464 Å and C1-O is 1.267 Å (Mau et al., 2003). Details of

the X-ray structure determinations and refinements are

provided in table 2. Based on these results the proposed

structure of ligand is given in Figure 3.

Fig. 2. FTIR spectrum of ligand.

Fig. 3. Molecular structure of ligand with partial numbering scheme.

Characterization by 1H NMR

1H NMR spectra was recorded in d6-DMSO solution

using TMS as an internal standard. 1H NMR spectrum

of Ligand; reveals the presence of aromatic protons at

8.34 (1H,d), 8.48 (1H,d), 8.37 (1H,d), 8.16 (1H,d),

7.24 (1H,d), 6.27 (1H,d), 6.29 (1H,s) ppm,

azomethine proton at 7.29 (1H,s) ppm, methyl

protons at 1.12(3H,t) ppm. Similarly two doublet

protons exhibited at 7.8-8.4 are assigned for the

naphthalene. The spectra is shown in fig. 4 (Charity et

al., 2017).

J. Bio. Env. Sci. 2018

81 | Sadia et al.

Fluorescence studies

The fluorescence intensity of the ligand and its Metal

complexes were studied in acetonitrile.

The sensing ability of ligand was studied by mixing it

with alkali, alkaline and transition metals to

investigate the effect of tested metal on the

fluorescence intensity of the ligand.

Fig. 4. H1 NMR spectra of the ligand.

The ligand did not show any remarkable fluorescence

separately. Upon excitation at 270 nm, the free

ligand, shows very weak fluorescence intensity in the

range 685-727 nm with λem at 365 nm. Upon addition

of an equivalent of metal to the solution of ligand,

caused enhancement in fluorescence intensity of

ligand.

Upon formation of complex with manganese resulted

highest enhancement in fluorescence intensity at 365

nm as compared to other heavy metal as shown in

figure 5. The enhancement in fluorescence intensity is

due to metal chelation enhancement effect and the

proposed binding mode can be explained on the basis

of photoinduced electron-transfer (PET) inhibition

phenomenon.

The free ligand was almost non fluorescent due to

transfer of electron from hydroxyl oxygen atom to

phenyl ring. Complexation of manganese with ligand

blocked PET phenomenon, resulting in highly

efficient chelation-enhanced fluorescence effect,

therefore fluorescence intensity of ligand enhanced

remarkably at 365 nm upon formation of manganese

complex (Zhaochao et al., 2010).

UV- vis spectroscopic analysis

As the ligand was not soluble in 100% aqueous media

therefore acetonitrile was used as a co-solvent when

UV-vis spectra of ligand was taken in a mixed

aqueous media in the absence and presence of

different concentration of manganese in distilled

water.

J. Bio. Env. Sci. 2018

82 | Sadia et al.

Fig. 5. Fluorescence spectra of the ligand (15×10-6 M) upon addition of metal (200×10-6 M) with an excitation at

270 nm.

Fig. 6. UV absorption spectrum of the ligand (10×10-6 M) in acetonitrile.

The UV-vis spectrum of ligand exhibited

characteristic main absorption band in the range 290-

340 nm with λmax of 297 nm as shown in Fig.6. Upon

addition of manganese to ligand λmax shifts to 286 nm.

The shift in the λmax of ligand is indicative of the

coordination involving the hydroxyl and imine as a

receptor and manganese as an analyte as shown in the

Fig. 7. When various concentration of manganese

were added to the solution of ligand the absorbance at

286 nm was enhanced as shown in the Fig. 7.

Test samples were prepared by using 10×10-6 M

solution of ligand and various concentrations of

manganese.

Effect of manganese concentration

The sensing mechanism of ligand was studied from

the fluorescence intensity of ligand. A series of

experiments were conducted upon sequentially

adding different concentrations of manganese in the

range 2-110×10-6 M.

J. Bio. Env. Sci. 2018

83 | Sadia et al.

Fig. 7. The UV absorption spectrum of ligand-manganese complex, manganese (300×10-6 M) and ligand 10×10-6

M in acetonitrile, λmax is 286 nm.

Fig. 8. Fluorescence intensity at 365 nm as a function of manganese concentration in 10-6 M.

The free ligand exhibited a very weak fluorescence

intensity at 365 nm, when excited at 270 nm. Upon

addition of manganese resulted greatest enhancement

in fluorescence intensity at 365 nm due to inhibition

of PET phenomenon by giving linear fluorescence

response in the range 2-110×10-6 M. The results are

shown in figure 9 (Ji et al., 2005).

Effect of pH

The effect of pH on the fluorescence intensity of

ligand was studied in a wide pH range from 2 to 12 of

the solution. pH was adjusted by adding 1×10-2 M

sodium hydroxide and 25×10-2 M hydrochloric acid

and their fluorescence intensity at 365 nm was

examined as shown in figure 10.

It is cleared from these results that in acidic pH,

the fluorescence intensity was low, indicating

poor stability of complex due to protonation of

hydroxyl group. Fluorescence intensity was

enhanced with increasing pH due to

deprotonation of OH (Di et al.,2013).

J. Bio. Env. Sci. 2018

84 | Sadia et al.

Fig. 9. Enhancement in fluorescence intensity of ligand (10×10-6 M) in acetonitrile upon increasing

concentration of manganese (2-110×10-6 M) with an excitation at 270nm.

Fig. 10. Fluorescence intensity of ligand (10×10-6M) in the presence of manganese (20×10-6 M) as a function of

pH, λex=270 nm, λem=365 nm.

Effect of reaction time on fluorescence intensity of

ligand

To investigate the effect of reaction time on the

fluorescence intensity of ligand towards manganese,

the fluorescence of ligand-manganese complex was

monitored at different intervals of time. The

fluorescence intensity at 365 nm increased

remarkably in 120 s and further enhancement was not

pronounced with increasing reaction time as shown in

figure 11.

Therefore ligand can be used as selective fluorescent-

on ligand for real-time determination of manganese

(Jayaraman et al., 2014).

Job’s plot analysis for determining binding

stoichiometric ratio of ligand with manganese

For determination of binding stoichiometry of ligand-

manganese complexes, Job’s plot analysis was carried

out. For spectroscopic analysis equimolar solutions of

ligand and manganese were prepared and mixed in

J. Bio. Env. Sci. 2018

85 | Sadia et al.

different ratios by continuous increase of one

constituent with the similar decrease of second

constituent keeping total concentration constant at

300×10-6 M. The molar fraction of ligand was varied

from 0.1-0.9. Binding stoichiometry was determined

by plotting the graph between the molar fraction of

ligand and respective fluorescence emission intensity

at 365 nm. The results as shown in figure 12 show

that fluorescence intensity reached maximum when

molar fraction was 0.7 showing 2:1 binding

stoichiometry meaning two parts of ligand bind with

one part of manganese (Ahmed et al ., 2015).

Fig. 11. The time dependent fluorescence intensity of ligand 10×10-6 M and manganese 20×10-6 M, at room

temperature at 365 nm with λex at 270 nm.

Fig. 12. Job’s plot of ligand and manganese, [manganese] + [ligand] concentration is 300×10-6 M, λex is 270 nm

and λem is 365 nm.

Association constant determination

On the basis of 2:1 binding stoichiometry determined

by Job’s plot, the association constant (Ka) of ligand

with manganese was calculated from experiment of

manganese concentration effect on fluorescence by

Benesi–Hildebrand plot to be 4×106 M-1 as given in

figure 13. the method and materials was deleted. No

need of it here.

J. Bio. Env. Sci. 2018

86 | Sadia et al.

Comparison of the synthesized ligand with

previously reported ligands

A number of analytical properties of ligand were

compared with those of other previously reported

ligands for manganese determination. The

comparison results are summarized in Table 3.

It is evident that the present ligand exhibits better

linear range and lower limit of detection, compared to

other reported ligands in literature.

Manganese determination in water samples

The synthesized ligand was used for determination of

manganese in different water samples. High degree

selectivity possessed by the ligand for manganese,

makes it potentially useful for determination of trace

amount of manganese.

Fig. 13. Benesi-Hildebrand plot from fluorescence data of ligand (5×10-6 M) with manganese (2-20×10-6).

Fig. 14. Linear change in fluorescence intensities of ligand (12×10-6 M) at 365 nm upon addition of manganese

(2-10×10-6 M) in spiked water samples.

The water samples analysed include laboratory,

natural water sample taken from river Swat located in

the northern region of Khyber-Pakhtunkwa and

industrial waste water of steel industry.

J. Bio. Env. Sci. 2018

87 | Sadia et al.

The water samples were collected by routine methods,

preserved and stored in pre-washed polyethylene

bottles and were spiked and assayed. For

spectrofluorometric analysis, different concentrations

of manganese were added into water samples. The

results are shown in figure 14. Fluorescence

intensities were proportional to manganese

concentration with correlation value of R2= 0.96

(Tolpygin et al., 2012).

Recommendations

Manganese is more frequently of toxicological

concern because overexposure to the metal can lead

to progressive, permanent, neurodegenerative

damage, resulting in syndromes similar to idiopathic

Parkinson's disease, Cardiovascular toxicity, and

hepatotoxicity, therefore during experiments it

should be handle with care and all safety precautions

should be followed. As far as environment is

concerned, It is strongly recommended that the

government and industrialists should launch various

research projects in order to eliminate trace level of

manganese from the environment and the common

people should be made aware of manganese toxicity.

Conclusion

In conclusion, a novel Schiff base fluorescent turn-on

ligand was synthesized and was used for

determination of manganese in water samples with

high selectivity, sensitivity and lower limit of

detection.

The ligand coordinated to the manganese through

azomethine nitrogen and phenolic oxygen atoms. Due

to PET inhibition phenomenon the ligand shows

coordination with manganese. Relative standard

deviation (RSD) was found to be 0.31 % for 8

replicate analyses with 3.8 × 10-6 M limit of detection.

References

Ahmed M, Abu D, Ibrahim MA. 2015. A review

on versatile applications of transition metal

complexes incorporating Schiff bases, Journal of

Applied Sciences 4, 119-133.

Arpi M, Georgina M, Arabinda M, Nitin C,

Samiran M. 2006. Synthesis, structures and

fluorescence of nickel, zinc and cadmium complexes

with the N,N,O-tridentate Schiff base N-2-

pyridylmethylidene-2-hydroxy-phenylamine

Polyhedron 25, 1753–1762.

Aschner M, Lukey B, Tremblay A. 2006. The

Manganese Health Research Program (MHRP):

Status report and future research needs and

directions Neuro Toxicology 27, 733–736.

http://dx.doi.org/10.1016/j.neuro.2005.

Castro MI, Méndez-Armenta M. 2008. Heavy

metals: Implications associated to fish consumption

Environmental Toxicology and Pharmacology 26.

www.dx.doi.org/10.1016/j.etap.2008.06.001263–271.

Charity W, Dikio1, Ikechukwu, Ejidike1,

Fanyana M, Mtunzi1, Michael J, Klink, Ezekiel

Dikio D. 2017 hydrazide schiff bases of

acetylacetonate metal complexes: synthesis,

spectroscopic and biological studies international

journal of pharmacy and pharmaceutical sciences 12,

0975-1012.

Dayu W, Wei H, Zhihua L, Chunying D, Cheng

H, Shuo W, Dehui W. 2008. Highly Sensitive

Multiresponsive Chemosensor for Selective Detection

of Hg2+ in Natural Water and Different Monitoring

Environments Inorganic Chemistry Communications

47, 7190-7209.

http://dx.doi.org/10.1021/ic8004344

Di Z, Ruyi Z, Min W, Meimei C, Xubin W,

Yong Y, Yufen Z. 2013. A Novel Series

Colorimetric and Off–On Fluorescent Chemosensors

for Fe3+ Based on Rhodamine B Derivative Journal of

Fluorescence 23, 13–19.

http://dx.doi.org/10.1007/s10895-012-1118-1

Duruibe J, Ogwuegbu MO, Egwurugwu JN.

2007. Heavy metal pollution and human biotoxic

effects International Journal of Physical Sciences

2,112-118.

J. Bio. Env. Sci. 2018

88 | Sadia et al.

Ghaedi M, Tavallali H, Shokrollahi A, Zahedi

M, Montazerozohori M, Soylak M. 2009. Flame

atomic absorption spectrometric determination of

zinc, nickel, iron and lead in different matrixes after

solid phase extraction on sodium dodecyl sulphate

(SDS)-coated alumina as their bis (2-

hydroxyacetophenone)-1, 3-propanediimine chelates

Journal of Hazardous Materials 166.

http://dx.doi.org/10.1016/j.jhazmat.2008.12

Hosseini M, Dehghan S, Ganjali Faridbod F.

2011. Determination of zinc(II) ions in waste water

samples by a novel zinc sensor based on a new

synthesized Schiff's base Materials Science and

Engineering C 31, 428–433.

http://dx.doi.org/10.1016/j.msec.2010.10.020

Janelle C, Wei Z. 2004. Manganese toxicity upon

overexposure NMR in Biomedicine 17. 544–553.

Jayaraman D, Jayshreek K, Chebroluprao C.

2014. ability of hydroxynaphthylidene derivatives of

hydrazine towards Cu2+ Experimental and

computational studies Journal of Chemical Sciences

126, 1135–1141.

http://dx.doi.org/10.1007/s12039-014-0648-2

Ji YK, Yun JJ, Yoon JL, Kwan MK, Mi SS,

Wonwoo N, Juyoung Y. 2005. A Highly Selective

Fluorescent Chemosensor for Pb2+ Journal of the

American Chemical Society 127. 10107-10111.

http://dx.doi.org/10.1021/ja051075b.

Lina W, Wenwu Q, Weisheng L. 2010. A

sensitive Schiff-base fluorescent indicator for the

detection of Zn2+ Inorganic Chemistry

Communications 13, 1122–1125.

http://dx.doi.org/10.1016/j.inoche.2010.06.021

Mau SR, Rahul B, Siddhartha C, Lara R,

Gabriele B, Gurucharan M, Ashutosh G. 2003.

Synthesis, characterization and X-ray crystal

structure of copper (II) complexes with

unsymmetrical tetra dentate Schiff base ligands

firstevidence of Cu (II) catalysed rearrangement of

unsymmetrical to symmetrical complex, Polyhedron

22, 617-624.

http://dx.doi.org/10.1016/S0277-5387(02)01435-3

Mengyu Z, Wei L, Jinting Z, Ganhong D,

Liming J, Jun L, Zhiquan S. 2014. A simple and

effective fluorescent chemosensor for the cascade

recognition of Zn2 and H2PO4 ions in protic media

Tetrahedron 70, 1011-1015.

http://dx.doi.org/10.1016/j.tet.2013.10.099

Morteza H, Zahra V, Mohammad RG,

Farnoush F, Shiva D, Kamal A, Masoud SN .

2010. Fluorescence “turn-on” chemosensor for the

selective detection of zinc ion based on Schiff-base

derivative Spectrochimica Acta Part A 75, 978–982.

http://dx.doi.org/10.1016/j.saa.2009.12.016

Nagesh GY, Mruthyunjayaswamy B. 2014.

Synthesis, Characterization and Biological Relevance

of Some Metal (II) Complexes with Oxygen, Nitrogen

and Oxygen (ONO) donor Schiff base Ligand derived

from Thiazole and 2-hydroxy-1-naphthaldehyde

Jurnal of molecular structure 12, 58- 67.

http://dx.doi.org/10.1016/j.molstruc.2014.12.058

Rajesh KS, Madhoolika A. 2005. Biological effects

of heavy metals An overview Journal of

Environmental Biology 26, 301-313.

Subhra B, Soma S, Marschner C, Baumgartner

J, Stuart R, Batten, David R, Samiran M. 2008.

Synthesis, crystal structures and fluorescence

properties of two new di- and polynuclear Cd (II)

complexes with N2O donor set of a tridentate Schiff

base ligand Polyhedron 27, 1193–1200.

Tianzhi Y, Kai Z, Yuling Z, Changhui Y, Hui Z,

Long Q, Duowang F, Wenkui D, Lili C,

Yongqing Q. 2008. Synthesis, crystal structure and

photoluminescent properties of an aromatic bridged

Schiff base ligand and its zinc complex, Inorganica

Chimica Acta 361, 233–240.

http://dx.doi.org/10.1016/j.ica.2007.07.012

Tolpygin IE, Mikhailenko NV, Bumber AA,

Shepelenko EN, Revinsky UV, Dubonosov AD,

Bren VA, Minkin VI. 2012. 11-R-Dibenzo[b,e]

[1,4] diazepin-1-ones, the Chemosensors for

Transition Metal Cations Russian Journal of General

Chemistry 82, 1243–1249.

http://dx.doi.org/10.1134/S1070363212070109

J. Bio. Env. Sci. 2018

89 | Sadia et al.

Ya JC, Pei JH, Chin FW, An TW. 2014. A highly

selective fluorescence turn-on and reversible sensor

for Al3+ ion Inorganic Chemistry Communications

39, 122–125.

http://dx.doi.org/10.1016/j.inoche.2013.11.019

Zhaochao X, Juyoung Y, David R. 2010. Spring

Fluorescent chemosensors for Zn2+ Chemical

Society Reviews 39, 1996–2006.

http://dx.doi.org/10.1039/B916287A

Ziyad AT, Abdulaziz M, Ajlouni K, Al-Hassan

A, Ahmed K, Hijazi A. 2011. Syntheses,

characterization, biological activity and fluorescence

properties of bis-(salicylaldehyde)-1, 3-

propylenediimine Schiff base ligand and its

lanthanide complexes Spectrochimica Acta Part A 81,

317–323.

http://dx.doi.org/10.1016/j.saa.2011.06.018